The fluorescence quenching of protonated β-carbolines has been investigated in acidic aqueous solutions and in w/o microemulsions using I(-), Br(-), Cu(2+), SCN(-), and Pb(2+) as quenchers. It was found that fluorescence quenching by these compounds is much more efficient in water than in microemulsions since quenching in microemulsions depends on the simultaneous occupancy of the water droplets by both fluorophore and quencher. Linear Stern-Volmer plots were obtained in all cases, leading to quenching rate constants of ca. 10(8)-10(10) M(-1) s(-1) in water and ca. 10(7)-10(8) M(-1) s(-1) in microemulsions. In the case of quenching by SCN(-), ns flash photolysis studies indicate formation of (SCN)2(˙-) showing that at least part of the quenching process involves an electron transfer mechanism. This indicates that the singlet excited states of the protonated β-carbolines can act as relatively strong oxidants (E° > 1.6 V), capable of oxidizing many species, including the biologically relevant DNA base guanine. The observation of the (SCN)2(˙-) transient in microemulsions demonstrates that it is possible to have the protonated β-carboline and at least two thiocyanate ions in the same water pool.
In this work, the adsorption of crystal violet dye from aqueous solution on charcoal and rice husk has been investigated, where the impact of variable factors (contact time; the dosage of adsorbent, pH, temperature, and ionic strength) have been studied. It has been found that charcoal and rice husk have an appropriate adsorption limit with regards to the expulsion of crystal violet dye from fluid arrangements. The harmony adsorption is for all intents and purposes accomplished in 45 min for charcoal and 60 min for rice husk. The amount of crystal violet dye adsorbed (0.4 g of charcoal and 0.5 g of rice husk) increased with an increasing pH and the value of 11 is the best. The effect of temperature on the adsorption process was studied at the range (298-323) K. The test comes about were broken down by utilizing Freundlich and Tempkin isotherm models, where the Freundlich and Tempkin factors were determined, and it has been found that the adsorption isotherm obey the Freundlich isotherm. The effect of ionic strength on the adsorption process was studied also via sodium chloride electrolyte solution; the results have been revaled that the sodium ion has a positive impact on the adsorption process. The thermodynamic parameters are shown estimated as ∆H values were 2.8012 kJ mol -1 and 5.8252 kJ mol -1 for charcoal and rice husk, respectively; this behavior referred to endothermic adsorption.
New mixed ligand complexes have been prepared by the reaction of Quinoline-2-Carboxylic Acid (HL1) and 4,4 ⁄ -dimethyl,2,2 ⁄ -Bipyridyl (L2) with Co(II),Ni(II) Cu(II), Zn(II), Pd(II) and Au(III) ions. The newly prepared complexes were isolated and characterized by (FT-IR) and (UV-Vis) spectroscopy, elemental analysis, flame atomic absorption technique, thermo gravimetric analysis, in addition to magnetic susceptibility and conductivity measurements. A theoretical treatment of these ligands and prepared complexes in gas phase were studied using Hyper chem.8 program, moreover, ligands in gas phase also have been studied using Gaussian program (GaussView Currently Available Versions (5.0.9) along with Gaussian 09 which is the latest in the Gaussian series of programs).
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